[Cython] Surprising behaviour wrt. generated tp_clear and tp_dealloc functions

[Torsten Landschoff]

Hi Stefan,

On 07/14/2013 10:39 AM, Stefan Behnel wrote:
> Torsten Landschoff, 11.07.2013 00:10:
>> I attached my current (trivial) patch. Currently I only support a decorator
>>
>>     @cython.noclear
>>     cdef class ...
>>
>> to inhibit generation of tp_clear.
> Thanks, looks ok to me. Please open a pull request on github for it.
I'd like to remove some code duplication I introduced in my changes and
add the feature to exclude specific attributes from clearing.
>> Before I continue with this approach I am wondering about the API. Is
>> noclear usable as a name? I think not because nobody will know what it
>> is talking about.
> I think that name is as good as any. It could be "no_gc_clear", if you find
> that clearer. It hints at GC, at least. I think that should be part of the
> name somehow.
Agreed.
So there will be the following decorator:

@cython.no_gc_clear
class ...

to disable generation of the clear method and

@cython.no_gc
class ...

to disable GC entirely. Okay for you?

I'd also like to support

@cython.no_gc_clear("keepthis", "keepthat")

to omit specific attributes from clear handling. I am not sure though
how to declare that decorator in directive_types. Would something like
this work:

    directive_types = {
        'final' : bool,  # final cdef classes and methods
        # ...
        'no_gc_clear': one_of('bool', 'list'),
        # ...
    }

?? How would I tell the parser that it should accept the strings as
*args of the decorator (if you know what I mean)?
> Please also document it somewhere in the extension types doc section (in
> the user guide):
>
> https://github.com/cython/cython/blob/master/docs/src/userguide/extension_types.rst
Thanks for the pointer, I was wondering about the right documentation
set to change.

Greetings, Torsten

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